The present invention relates to a photosensitive composition suitable for use in making a lithographic plate, IC circuit or photomask. In particular, the present invention relates to a photosensitive composition comprising a positive working photosensitive compound and a polymeric compound having an excellent abrasion resistance.
Among positive working photosensitive compositions, a composition comprising an o-naphthoquinonediazide compound and a novolak-type phenolic resin is quite excellent and has been used in the preparation of a lithographic plate or as a photoresist on an industrial scale.
However, the use of this composition is still limited, because it has defects, due to the properties of novolak phenolic resin used as the main component, such as poor adhesion to the support, brittleness of the film, poor coating property, low abrasion resistance, and poor printing durability when it is used in the production of a lithographic plate.
To solve these defects, various polymeric compounds has been investigated as a binder. For example, polyhydroxystyrene or hydroxystyrene copolymers as described in Japanese Patent Publication for Opposition Purpose (hereinafter referred to as `J. P. KOKOKU`) No. 52-41050 provide improved film-forming properties. However, they are poor in respect of abrasion resistance. Further, it is proposed to use, as a binder, a polymeric compound having structural units of an acrylic acid derivative in the molecular structure in Japanese Patent Unexamined Published Application (hereinafter referred to as `J. P. KOKAI`) No. 51-34711. However, such a polymeric compound makes narrow the allowance of suitable developing conditions and provides an insufficient abrasion resistance.
Another known polymer having an excellent abrasion resistance is a polyurethane resin. A combination of a positive working diazo compound with a substantially linear polyurethane resin is described in U.S. Pat. NO. 3,660,097. However, this polyurethane resin has no alkali-soluble group essentially and therefore has an insufficient solubility in an aqueous alkali developer. It is thus quite difficult to conduct the development in such a manner that the photosensitive layer can be completely removed from the non-image area (exposed area).
A photosensitive composition comprising an anionic polyurethane resin is described in J. P. KOKAI NO. 61-20939. This anionic polyurethane resin is water-soluble and, therefore, is essentially different from the water-insoluble polyurethane resin of the present invention and has an insufficient solubility in coating organic solvent. Another defect of the anionic polyurethane resin is to deteriorate the stability of the diazo compounds.
A positive working photosensitive composition comprising a polyurethane resin having a carboxyl group is described in U.S. Pat. No. 4,898,803 and a photosensitive composition comprising a polyurethane resin having an acidic hydrogen such as N-sulfonylamido or N-sulfonylurethane group is described in J. P. KOKAI No. 63-261350. Although they are soluble in the aqueous alkali developer and have an excellent abrasion resistance, the adhesion thereof to an aluminum support is not always sufficient. Therefore, the photosensitive layer is sometimes peeled off from the support depending on the storage conditions.